1. Technical Field
This invention relates generally to radio controlled (R/C) models, and more particularly to an R/C speed controller with an audible feedback signal.
2. Background Information
Recall that the drive motor of a radio controlled model operates under control of an onboard control module called an R/C speed controller . . . or just speed controller. The speed controller includes circuitry that controls the drive motor according to setpoint information received by a miniature onboard receiver. The R/C enthusiast manipulates a throttle trigger on a handheld transmitter to produce the setpoint information, the transmitter communicates it to the speed controller via the onboard receiver, and the speed controller controls the drive motor accordingly.
To calibrate some existing speed controllers and fine tune operation for maximum racing performance, the operator adjusts various potentiometers on the speed controller. One potentiometer calibrates the speed controller to the setpoint representing zero motor speed. Another calibrates it to the setpoint representing maximum motor speed. A third, sets a limit on the maximum drive current the motor can draw. Other such setup adjustments may be involved, and the operator must often use separate metering instruments. So, the tuning procedure (i.e., speed controller setup) can be somewhat tedious and not easily repeated from one race to the next.
U.S. patent application Ser. No. 783,279 (the parent application) facilitates setup by providing microprocessor circuitry and a miniature keypad on the speed controller. The microprocessor responds to keypad entries by making desired setup adjustments. As a result, the operator can enter operating parameters directly, and even store and recall information as desired, all without potentiometers, test points, and separate metering instruments.
Preferably, the microprocessor circuitry includes means for producing an audible feedback signal in order to indicate when a keypad entry has been successfully made or a desired operation fully performed. But that requirement introduces certain problems. Buzzers, piezoelectric devices, and other existing electrical-to-acoustical transducers require too much additional space in an already fully packed, miniaturized, speed control module. Furthermore, they introduce undesirable weight and cost. Thus, R/C speed controllers need a better way to produce an audible feedback signal.